Arteriolar to venular red cell and plasma dispersion in hemorrhage- and endotoxin-shocked cats
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Abstract:
The passage of red cells is more rapid than for plasma through the microcirculation of most tissues. The effects of hemorrhage (13 ml/kg) and endotoxin (3 mg/kg) on this phenomenon were studied in the exposed mesentery of cats anesthetized with Dial-urethane using epi-illumination fluorescence or transillumination television microscopy. Femoral artery pressure, arteriolar pressure, and arteriolar and venular diameters were measured. FITC-dextran, the plasma label, and DTAF-labeled red cells (DTAF-RBCs) or sulphemoglobin-labeled RBCs (SH-RBCs) were injected as a bolus (0.005 ml in 0.5 seconds) into a small branch of the mesenteric artery at control and after the experimental procedure. Animals were hemorrhaged from the left femoral artery (13 ml/kg) or injected IV with endotoxin. Time-concentration curves were recorded from video tape recordings of the passage of the indicator by videodensitometry for determination of the mean transit times (t). During hemorrhage and endotoxin the arterial pressure decreased significantly as did the arteriolar flow velocity. Following hemorrhage arteriolar and venular diameters and arteriolar pressures decreased significantly. Postendotoxin, arteriolar and venular diameters increased and arteriolar pressures did not decrease significantly. During control the t of labeled red cells was exceeded significantly by those of FITC-dextran in all microvascular segments. Following hemorrhage the t of the two indicators were increased significantly but were not significantly different in the arterioles. However, they were different in the venules. One hour after endotoxin t was significantly increased in all segments and further increased at three hours. However, the labeled red cell values were still exceeded by the FITC-dextran values at both times. It would appear that the differences in t would be abolished by vasoconstriction reducing axial streaming and plasma skimming whereas vasodilation does not change these phenomena.